Infra-red radiant electric heaters incorporating infra-red lamps have been described, for example in patent specifications GB 1 273 023, EP 0 117 346 and GB 2 146 431. Such heaters are typically incorporated in cookers and cooktops having a flat, glass ceramic cooking surface. The type of lamp used comprises a tungsten filament supported inside a tubular envelope of fused silica, with electrical connections brought out through hermetic pinch seals at the ends of the envelope. In these heaters the infra-red lamps extend above a reflecting surface and are fixed in position by sandwiching both ends of the lamp envelope in the heater periphery or by bolting the electrical connections to a bracket. Although sandwiching the ends of the envelope is a satisfactory arrangement in the case of relatively short, straight lamps, it would not provide sufficient support in the case of other configurations such as the generally circular lamp shown in GB 1 273 023. In this latter case the lamp would be cantilevered, with the risk of excessive stress being applied to the lamp envelope. Bolting the electrical connections is even less desirable, since it subjects the hermetic pinch seal between the connections and the envelope to considerable stress, especially in the configuration of GB 1 273 023.
Nonetheless, a need exists for lamp configurations other than the existing short, straight arrangements. Such arrangements suffer from the disadvantage of emitting the radiation only from restricted portions of the overall heater area, and these portions do not have an optimum shape. This makes it difficult to provide a heated area with an appropriate distribution of radiation.
However, at present only short, straight lamps provide sufficient strength and rigidity of mounting to withstand typical use and more particularly the impact tests which such heaters are required to survive as a precaution against damage during transport, storage and use. It is easy to see for example that a heater with a circular lamp supported only at its (adjacent) ends, as in GB 1 273 023, would be very vulnerable to fracture of the lamp if it were dropped or subjected to shock from a utensil falling onto a glass ceramic cooking surface above the heater.
It is an object of this invention to provide a heater incorporating a lamp which may not be straight but is nonetheless adequately supported.